The present invention is in the field of cryogenic propellants and densification processes and systems therefor.
This invention relates to the densification of liquids. More specifically, this invention relates to the densification of cryogenic propellants at or above atmospheric pressure.
The densification of cryogenic propellants is anticipated to become more necessary in the future to maximize fuel loading and payloads. At that time, there will be a demand for densification systems that will function with maximum efficiency and minimum overall cost. These densification systems are particularly of interest to aerospace companies and government agencies involved in launch site construction.
Present processes for cryogenic propellant densification are based on heat exchange with cryogenic fluids boiling under reduced pressure, achieved with the use of expensive and difficult-to-control compressor systems. These densification systems require large banks of submerged coils with trains of vacuum pumps or expensive cold blowers to produce the required reduced pressures. It is therefore desirable to develop a system avoiding these problems and costs by operating at or above atmospheric pressure. Estimates indicate that such a system would have significantly reduced capital investment and operating costs coupled with improved reliability and availability.
It is therefore an object of the present invention to develop a method and system for densifying cryogenic propellants at or above atmospheric pressure.
Although described with respect to the fields of cryogenics and propellants, it will be appreciated that similar advantages of liquid densification at or above atmospheric pressure may obtain in other applications of the present invention. Such advantages may become apparent to one of ordinary skill in the art in light of the present disclosure or through practice of the invention.
The present invention includes densification apparatus, densification devices, and densification systems. The invention also includes machines or electronic devices using these aspects of the invention. The present invention may also be used to upgrade, repair or retrofit existing machines or electronic devices or instruments of these types, using methods and components known in the art. The present invention also includes methods for achieving such densification.
The heat exchanging elements or devices that may be used in the systems and methods of the present invention may include counterflow heat exchangers and vapor phase heat exchange chambers. Accordingly, it will be understood that any appropriate heat exchanging element(s) may be used in the systems and methods of the present invention in accordance with the appropriate temperature change, phase and mass flow characteristics of the fuel to be densified, as will be appreciated from the examples presented herein. Accordingly, the heat exchanging elements that may be used in the systems and methods of the present invention may include counterflow heat exchangers (such as plate fin heat exchangers, such as those commercially available from such companies as Chart Corporation of Mayfield Heights Ohio, Sumitomo Precision Products of Japan, and Marsten-Palmer of the United Kingdom), and vapor phase heat exchange chambers. The systems and methods of the present invention may use vapor heat exchange chambers such as packed towers. The preferred vapor heat exchange chamber used in the systems and methods of the present invention is a packed heat exchange tower, using commercially available tower packing materials commonly used in the chemical industry.
Accordingly, it will be understood that in the following summary and detailed description reference to heat exchangers or packed towers may also include alternative heat exchange elements as generally described above.
The systems and methods of the present invention may be respectively operated and conducted in order to produce densified cryogenic propellants such as liquid oxygen and/or liquid hydrogen. Thus, the present invention relates to a system for densifying and subcooling liquid oxygen and/or hydrogen.
One of the advantages of the systems and methods of the present invention is that they may be respectively operated and conducted at or just slightly above ambient atmospheric pressure.
One system utilizes a conduit adapted to carry flows of liquid, preferably liquid oxygen, liquid nitrogen, and liquid hydrogen. To avoid direct contact of hydrogen and oxygen, a first heat exchanger is used to allow only thermal interaction of the liquid oxygen and liquid nitrogen. The liquid oxygen and liquid nitrogen flow in opposing directions through the first heat exchanger. The first heat exchanger cools and thereby densifies the liquid oxygen.
A second heat exchanger is preferably also used, adapted to allow thermal interaction of the liquid nitrogen with the liquid hydrogen. The liquid nitrogen and liquid hydrogen preferably flow in opposing directions through the second heat exchanger that is controlled so that the liquid hydrogen is vaporized through the thermal interaction before leaving the second heat exchanger. The second heat exchanger is preferably adapted to cool the liquid nitrogen.
A packed tower is used, in conjunction with or without the second heat exchanger, adapted to allow thermal interaction of the liquid nitrogen with the liquid or gaseous hydrogen, the liquid nitrogen and hydrogen flowing in opposing directions through the packed tower. The packed tower allows the liquid hydrogen to cool the liquid nitrogen by evaporation and thermal interaction before leaving the packed tower. The packed tower is then adapted to release any vaporized gas comprising the nitrogen and hydrogen.
The system may also recirculate the liquid nitrogen from the first heat exchanger back to the packed tower. The cooled liquid nitrogen is preferably directed from the second heat exchanger to the first heat exchanger. The vaporized hydrogen is preferably directed from the second heat exchanger into the packed tower in order to aid in cooling the liquid nitrogen passing through the tower. The system may also use one or more pumps to generate fluid flow and recirculate the liquid nitrogen.
Also included in the present invention is a system for simultaneously densifying and subcooling liquids, preferably liquid oxygen and liquid hydrogen. The system utilizes conduit adapted to carry flows of liquid oxygen, liquid nitrogen, liquid hydrogen, and liquid helium.
The system uses a first packed tower, adapted to allow thermal interaction of the helium and liquid hydrogen. The liquid or gaseous helium and liquid hydrogen flow in opposing directions through the packed tower, adapted so that the liquid hydrogen is cooled by evaporation and thermal interaction before leaving the packed tower. The first packed tower is also adapted to direct any vaporized gas of the helium and hydrogen out of the packed tower.
A first heat exchanger is preferably used, adapted to allow thermal interaction of the liquid hydrogen with the liquid helium. The liquid hydrogen and liquid helium flow in opposing directions through the first heat exchanger, preferably controlled so that the liquid helium is vaporized through the thermal interaction before leaving the first heat exchanger. The first heat exchanger is preferably also adapted to cool the liquid hydrogen. The portion of the system mentioned thus far may be used alone if only hydrogen is to be densified.
In the dual-fluid densification system, a second heat exchanger is preferably used to allow thermal interaction of the liquid nitrogen with the vaporized hydrogen and vaporized helium. The liquid nitrogen is adapted to flow through the second heat exchanger in a direction opposite the flow of vaporized hydrogen and helium. The second heat exchanger is adapted to cool the liquid nitrogen.
A second packed tower is used, adapted to allow thermal interaction of the liquid nitrogen with the vaporized hydrogen and helium. The liquid nitrogen flows through the second packed tower in a direction opposite the flow of vaporized hydrogen and helium, adapted so that the liquid nitrogen is cooled by evaporation and thermal interaction before leaving the packed tower. The second packed tower is also adapted to release from the system any vaporized gas comprising the nitrogen, helium, and hydrogen.
The system uses a third heat exchanger, adapted to allow thermal interaction of the liquid oxygen with the liquid nitrogen. The liquid oxygen flows through the third heat exchanger in a direction opposite the flow of liquid nitrogen. The third heat exchanger is adapted to cool the liquid oxygen.
The system may also recirculate the liquid nitrogen, from the third heat exchanger back to the second packed tower. The cooled liquid nitrogen is preferably directed from the second heat exchanger to the third heat exchanger, where it is used to cool the liquid oxygen. The system may use one or more pumps to generate liquid flow.
The invention also includes a method of densifying a liquid, preferably liquid oxygen. In the method, a flow of liquid oxygen is passed through a first heat exchanger. A flow of liquid nitrogen is also passed through the first heat exchanger, in a direction opposite the flow of liquid oxygen. The first heat exchanger is adapted to allow thermal interaction of the liquid oxygen with the liquid nitrogen. The first is heat exchanger is adapted so that the flow of liquid oxygen is cooled so as to densify the liquid oxygen.
The method also involves passing the flow of liquid nitrogen exiting the first heat exchanger through a packed tower. The packed tower has a flow of vaporized or liquid hydrogen running in a direction opposite the flow of liquid nitrogen that is allowed to thermally interact with the liquid nitrogen, whereby the liquid nitrogen may be cooled by evaporation before exiting the packed tower. The packed tower is adapted to vent any vaporized nitrogen or vaporized hydrogen from the packed tower.
A preferred step involves passing the cooled liquid nitrogen exiting the packed tower and a flow of liquid hydrogen through a second heat exchanger. The flow of liquid hydrogen is passed through the heat exchanger before entering the packed tower as vaporized hydrogen, the flow of liquid hydrogen passed through the heat exchanger in a direction opposite the flow of liquid nitrogen. The second heat exchanger is adapted to allow thermal interaction of the liquid hydrogen with the liquid nitrogen, controlled so that the liquid hydrogen is vaporized through the thermal interaction before leaving the second heat exchanger. The second heat exchanger is also adapted to cool the liquid nitrogen before the cooled liquid nitrogen is passed to the first heat exchanger.
The method may additionally comprise the step of capturing the flow of densified liquid oxygen exiting the first heat exchanger. Another step may involve venting the flow of vaporized hydrogen and vaporized nitrogen to atmosphere.
The present invention also includes a method for simultaneously densifying two liquids, preferably liquid oxygen and liquid hydrogen The preferred method involves passing a flow of liquid hydrogen through a first packed tower. A flow of liquid or gaseous helium is also passed through the first packed tower, the helium flowing through the first packed tower in a direction opposite the flow of liquid hydrogen. The first packed tower is adapted to allow thermal interaction of the helium with the hydrogen. The first packed tower additionally allows any vaporized hydrogen or vaporized helium to pass from the tower. The first packed tower is also adapted so that the flow of liquid hydrogen is cooled by evaporation, so as to densify the liquid hydrogen.
The method preferably also involves passing the cooled liquid hydrogen exiting the first packed tower and the flow of liquid helium through a first heat exchanger. The first heat exchanger is preferably adapted to allow thermal interaction of the liquid hydrogen with the liquid helium. The liquid hydrogen and liquid helium flow in opposing directions through the first heat exchanger, preferably controlled so that the liquid helium is vaporized through the thermal interaction before leaving the first heat exchanger. The first heat exchanger is preferably also adapted to cool the liquid hydrogen. The steps mentioned thus far may be practiced by themselves if hydrogen alone is to be densified.
Other steps in the two-liquid densification method involve passing a flow of liquid nitrogen through a second packed tower, along with passing the flow of vaporized hydrogen and vaporized helium through the second packed tower. The vaporized hydrogen and vaporized helium are allowed to flow through the second packed tower in a direction opposite the flow of liquid nitrogen, adapted to allow thermal interaction of the vaporized hydrogen and vaporized helium with the liquid nitrogen. The second packed tower is adapted so that any vaporized hydrogen, helium, or nitrogen is passed from the tower. The second packed tower also allows the flow of liquid nitrogen to be cooled before exiting the tower.
The method preferably also involves passing the flow of cooled liquid nitrogen exiting the second packed tower and the flow of vaporized hydrogen and vaporized helium through a second heat exchanger. The flow of vaporized hydrogen and vaporized helium are passed through the second heat exchanger before entering the second packed tower. The flow of liquid nitrogen is passed through the second heat exchanger in a direction opposite the flow of vaporized hydrogen and vaporized helium, adapted to allow thermal interaction of the liquid nitrogen with the vaporized hydrogen and vaporized helium. The second heat exchanger is adapted to further cool the liquid nitrogen.
Other steps in the method involve passing a flow of liquid oxygen through a third heat exchanger, along with passing the flow of cooled liquid nitrogen through the third heat exchanger. The liquid nitrogen flows through the third heat exchanger in a direction opposite the flow of liquid oxygen, adapted to allow thermal interaction of the liquid oxygen with the liquid nitrogen. The third heat exchanger is adapted so that the flow of liquid oxygen is cooled before exiting the third heat exchanger, such that the liquid oxygen is densified. The flow of liquid nitrogen is then directed back into the second packed tower.
The method may additionally comprise the step of capturing the flow of densified liquid hydrogen exiting the first heat exchanger. The flow of densified liquid oxygen exiting the third heat exchanger may also be captured. The method may additionally involve venting the flow of vaporized hydrogen, helium, and nitrogen to atmosphere.
The densified cryogenic propellants produced in accordance with the methods of the present invention may be conducted into any appropriate container. For instance, the propellants may be dispensed directly into the fuel tanks of a rocket engine. Preferably, the densified cryogenic propellants are circulated into and out of the rocket fuel tank so as to allow for the fuel tank to be cooled such that the densified cryogenic propellants may reach their maximum possible densified state within the rocket fuel tank(s). Accordingly, the systems of the present invention include conduits to supply the densified fuel to a rocket engine fuel tank (or tanks), and preferably to recirculate the densified fuel into an out of the rocket engine fuel tank(s). The present invention thus also includes a system as described above attached by conduits to one or more rocket engine fuel tanks, preferably at the launch site of a rocket.